With the Black Death raging throughout Switzerland, poison was reported to have been found in the wells at Zofingen. Some Jews were put to the "Dümeln" (thumbscrews) test, whereupon they "admitted" their guilt of the charges brought against them. This discovery was then communicated to the people of Basel, Zurich, Freiburg-im-Breisgau, and even Cologne.

The Jews of Basel were burned on an island in the Rhine on January 9, 1349, in wooden huts that were especially built for the occasion. Their children, who were spared, were taken and forcibly baptized.